In typical prior art arrangements, in order to adjust a movable rail of a window covering such as a shade or blind that is skewed (not horizontal or not parallel to the head rail) after installation, the operator must disengage at least one of the lift cords from the skewed rail (such as a movable bottom rail or a movable intermediate rail), adjust the length of the lift cord, and reattach the lift cord to the rail. This is generally not something the end user is capable of doing, and it may even present a challenge to a seasoned installer.
U.S. Pat. No. 8,944,135 to Spray (“the Spray '135 Patent”), which is hereby incorporated by reference herein in its entirety for all purposes, discloses a skew adjustment mechanism that adjusts the length of the lift cord at the end of the cord opposite the lift spool (the anchor end of the lift cord). The anchor end of the lift cord is secured to an anchor drum mounted for selective rotation within a housing. The lift spool rotates to extend and retract the lift cord as the movable rail moves up and down to extend and retract the window covering. The anchor spool is stationary as the movable rail moves up and down, but the anchor spool can be rotated manually to adjust the length of the lift cord to adjust for a skewed condition.
Column 2, lines 35-41, of the Spray '135 Patent states, “The drum is retained in selected positions relative to the housing with two separate retaining systems so that once the drum is set relative to the housing for a pre-selected length of the lift cord, it will substantially retain this position until the position is adjusted by overcoming the retaining systems with a screwdriver or other similar tool.” The two retaining systems include two sets of teeth one set directed radially and one set directed axially. Projections on the housing engage the teeth to provide a holding force that prevents the anchor drum from rotating once its position has been established by the user.
While the use of two retaining systems helps retain the anchor drum in the desired position, even two retaining systems may not be sufficient to prevent the anchor drum from rotating when the window covering is heavy and exerts substantial force on the anchor drum through the lift cord. Accordingly, an improved skew adjustment mechanism would be welcomed in the technology.